The invention relates to solid support reagents that are employed in methods and kits for the determination of analytes in samples, such as patient samples, known or suspected to contain one or more of the analytes.
In the fields of medicine and clinical chemistry, many studies and determinations of physiologically reactive species or analytes are carried out using conjugates involving specific binding pair members and supports and/or labels or the like. Various assay techniques that involve the binding of specific binding pair members are known. The analytes themselves are normally members of specific binding pairs, which allow for their detection employing a corresponding member of the specific binding pair to which the analyte in question belongs.
A variety of clinical conditions may be diagnosed and monitored by detecting the presence of and/or amount of a specific binding pair member analyte in a sample. The results of chemical, biochemical, and biological assays are used to make important decisions; and, therefore, the accuracy and reliability of the result is of utmost importance. Heretofore, control samples of known concentration are assayed periodically, or even simultaneously with the sample to be measured, to calibrate and verify the operation of the assay on the unknown sample. This process reduces, but does not eliminate, the possibility of error in the assay of interest.
As the importance of measuring the presence of an analyte in a sample has increased, a number of means have been developed to detect such analytes. One method involves the conjugation of a label to a specific binding pair member that is employed as an assay reagent to bind to the analyte. In other approaches, a specific binding pair member for the detection of the analyte is conjugated to a support, which is employed as an assay reagent in various ways along with other reagents to detect the analyte in question. Combinations of the above approaches are also utilized.
Assays in which a sample and one or more reagents are reacted in various ways to form a complex such as an antibody/antigen or similar complex, which may then be observed in order to measure the presence or level of an analyte or one or more of several analytes in the sample, are well known. Typically, in some embodiments an antibody is used to assay for the presence and/or amount of a hapten or an antigen for which the antibody is specific. The haptens and antigens include, for example, peptides, proteins, hormones, alkaloids, steroids, antibodies, nucleic acids, and fragments thereof, enzymes, cell surface receptors, and the like.
The usefulness of the assay reagent, however, will depend upon the specificity of the specific binding pair member for the other member, and also will depend upon the level of non-specific binding of the assay reagent or of the components of the assay reagent. The non-specific binding often reduces the sensitivity of the assay. The degree of non-specific binding limits the usefulness of an assay reagent. The greater the non-specific binding in a particular assay reagent, the lesser will be the sensitivity of the determination.
In one approach for reagents involving solid supports, a specific binding pair member such as, for example, an analyte analog, is linked directly to the solid support by covalent binding. Unfortunately, with such reagents, a not insignificant amount of non-specific binding of the specific binding pair member to the surface of the solid support is present. During storage and/or use of such a reagent, non-specifically bound conjugate leaches from the solid support and is present in a liquid assay medium. The presence of such non-specifically bound specific binding pair member leads to inaccuracies in the assay methods employed using the reagent. Non-specific binding refers to non-covalent binding between molecules that is relatively independent of specific surface structures. Non-specific binding may result from several factors including, e.g., hydrophobic interactions between molecules, physical adsorption to the porous surface of solid support, and the like.
There remains a need for assay reagents, which exhibit reduced non-specific binding when used in assays for the detection of one or more analytes. In particular, there remains a need for an assay reagent that comprises a solid support where an analog analyte that may be non-specifically bound to the solid support does not interfere in an assay conducted with such a reagent.